Mercruiser 3.0 fuel delivery issue

[Bszakaly97]

So back again with yet another issue, mercruiser 3.0 with points ignition... seems to run fine up to around 10 mph on lake with idle set kind of on the higher side anything after that starts to bog down and also sometimes stalling when putting into gear. So the story is is that the gas line from the tank I have a glass see through filter and no matter how much I prime it with the pump it never seems to fill like it used too. Sometimes the ball gets hard and won’t even let me pump any more fuel... so i got it to fill once by shaking primer pump around, caught plane for a minute or 2 and engine started cutting out. Looked back at filter and is empty no gas left in the line? I’m thinking either anti siphon valve on gas tank or feels like the ball in the primer ball is loose all over on the inside of ball? Any thoughts? Was dark by the time I decided to take gas cap off to see if that made any difference so not sure about that.

 

[Bondo]

Ayuh,..... There should Not be a primer bulb on an I/O application,....

Use a remote tank of fresh clean gas hooked to the fuel pump to verify that yer tank is the problem,.....

 

[nola mike]

Ayuh,..... There should Not be a primer bulb on an I/O application,....

Nor a glass inline filter. From what you're saying though, either bad fuel pump or restriction before the pump. I'd start by checking fuel pressure though. If you run on a remote tank and the motor works when squeezing the bulb I'd guess fuel pump.

 

[Bszakaly97]

Nor a glass inline filter. From what you're saying though, either bad fuel pump or restriction before the pump. I'd start by checking fuel pressure though. If you run on a remote tank and the motor works when squeezing the bulb I'd guess fuel pump.

Glass filter was out there so I can see what’s going on.. put small hose to pump and took line off carb and it’s pumping strong but when connected to tank filter goes empty and stops pulling gas even with cap off

 

[nola mike]

Glass filter was out there so I can see what’s going on.. put small hose to pump and took line off carb and it’s pumping strong but when connected to tank filter goes empty and stops pulling gas even with cap off

Not sure where you're putting the hose, input side of pump and then disconnected carb? And that flows, but when input side of pump is connected to tank it doesn't flow anymore?
If that's the case, you have a restriction between the tank and pump. Either anti-syphon valve, in tank filter/sock, water/fuel filter (if equipped), or fuel line itself (either plugged or collapsing under vacuum).